U.S. patent number 8,679,224 [Application Number 13/222,002] was granted by the patent office on 2014-03-25 for hydrogen, lithium, and lithium hydride production.
This patent grant is currently assigned to Babcock & Wilcox Technical Services Y-12, LLC. The grantee listed for this patent is Sam W. Brown, Peggy J. Campbell, Michael R. Phillips, G. Louis Powell, Larry S. Spencer. Invention is credited to Sam W. Brown, Peggy J. Campbell, Michael R. Phillips, G. Louis Powell, Larry S. Spencer.
United States Patent |
8,679,224 |
Brown , et al. |
March 25, 2014 |
Hydrogen, lithium, and lithium hydride production
Abstract
A method of producing high purity lithium metal is provided,
where gaseous-phase lithium metal is extracted from lithium hydride
and condensed to form solid high purity lithium metal. The high
purity lithium metal may be hydrided to provide high purity lithium
hydride.
Inventors: |
Brown; Sam W. (Knoxville,
TN), Spencer; Larry S. (Knoxville, TN), Phillips; Michael
R. (Harriman, TN), Powell; G. Louis (Oak Ridge, TN),
Campbell; Peggy J. (Clinton, TN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Brown; Sam W.
Spencer; Larry S.
Phillips; Michael R.
Powell; G. Louis
Campbell; Peggy J. |
Knoxville
Knoxville
Harriman
Oak Ridge
Clinton |
TN
TN
TN
TN
TN |
US
US
US
US
US |
|
|
Assignee: |
Babcock & Wilcox Technical
Services Y-12, LLC (Oak Ridge, TN)
|
Family
ID: |
47741725 |
Appl.
No.: |
13/222,002 |
Filed: |
August 31, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130047789 A1 |
Feb 28, 2013 |
|
Current U.S.
Class: |
75/589; 423/646;
423/658.2 |
Current CPC
Class: |
C22B
26/12 (20130101); C01B 3/04 (20130101); B01D
53/22 (20130101); C01D 15/00 (20130101); Y02E
60/36 (20130101); Y02E 60/364 (20130101) |
Current International
Class: |
C22B
26/12 (20060101); C01B 3/04 (20060101) |
Field of
Search: |
;75/589 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Soloveichik et al. Magnesium borogydride as a hydrogen storage
materials: properties and dehydrogenation pathway of unsolvated
Mg(BH4)2. International Journal of Hydrogen Energy, 2009, vol. 34,
p. 916-928. cited by examiner .
Jeppson et al. Lithium literature review: Lithium's properties and
interactions, Apr. 1978, p. 1-111. cited by examiner.
|
Primary Examiner: King; Roy
Assistant Examiner: Su; Xiaowei
Attorney, Agent or Firm: Renner, Esq.; Michael J. Luedeka
Neely Group, P.C.
Government Interests
GOVERNMENT RIGHTS
The U.S. Government has rights to this invention pursuant to
contract number DE-AC05-00OR22800 between the U.S. Department of
Energy and Babcock & Wilcox Technical Services Y-12, LLC.
Claims
What is claimed is:
1. A method of producing hydrogen and lithium comprising: heating
lithium hydride to form liquid-phase lithium hydride; reducing an
ambient pressure over the liquid-phase lithium hydride; extracting
hydrogen and gaseous-phase lithium metal from the liquid-phase
lithium hydride; condensing the gaseous-phase lithium metal as
purified solid-phase lithium metal; and melting the solid-phase
lithium metal to form refined liquid-phase lithium metal.
2. The method of claim 1 further comprising hydriding the refined
liquid-phase lithium metal.
3. The method of claim 1 further comprising: hydriding the refined
liquid-phase lithium metal to form re-charged lithium hydride; and
again performing the steps of claim 1 at least one time using the
re-charged lithium hydride as the lithium material.
4. The method of claim 1 further comprising retarding a formation
of a barrier crust adjacent the liquid-phase lithium hydride.
5. The method of claim 4 wherein the step of retarding the
formation of the barrier crust comprises sparging the liquid-phase
lithium hydride with an inert gas.
6. The method of claim 4 wherein the step of retarding the
formation of the barrier crust comprises agitating the liquid
lithium hydride with an energy having a periodic waveform.
Description
FIELD
This disclosure relates to the field of material processing. More
particularly, this disclosure relates to hydrogen, lithium and
lithium hydride production.
BACKGROUND
Lithium hydride (LiH) is a useful material. It reacts with water to
produce hydrogen gas and lithium hydroxide. Although this is a
violent reaction, it was used in World War II to provide a
lightweight source of hydrogen to inflate signaling balloons. In
addition to various applications that require the production of
hydrogen, there are many applications that require high purity
lithium and many applications that require the production of high
purity lithium hydride. Standard methods for production of high
purity lithium and high purity lithium hydride are generally
expensive. What are needed therefore are safer and more economical
means for using lithium hydride to produce hydrogen, and better
means for producing high purity lithium and high purity lithium
hydride.
SUMMARY
The present disclosure provides various embodiments of hydrogen,
lithium, and lithium hydride processing apparatuses. Typically
these apparatuses have a hot zone to heat solid-phase lithium
hydride to form liquid-phase lithium hydride. A vacuum source is
typically provided to extract hydrogen and gaseous-phase lithium
metal from the liquid-phase lithium hydride. Embodiments of the
apparatuses also typically have a cold zone to condense the
gaseous-phase lithium metal as purified solid-phase lithium metal.
A heater is typically provided to melt the purified lithium metal
in the cold zone and form refined liquid-phase lithium in the hot
zone. A moderate zone may be provided and is typically disposed
between the hot zone and the cold zone to capture a lithium
condensate portion of the gaseous-phase lithium and to return the
lithium condensate portion to the hot zone as liquid-phase lithium
condensate.
The present disclosure further provides methods of producing
hydrogen. The methods typically employ a step "a" of heating
lithium hydride to form liquid-phase lithium hydride, a step "b" of
extracting hydrogen from the liquid-phase lithium hydride, leaving
residual liquid-phase lithium metal, and a step "c" of hydriding
the liquid-phase lithium metal. The methods typically involve
repeating steps "a" and "b" at least once.
The present disclosure also provides methods of processing hydrogen
and lithium material. Methods typically include steps of heating a
lithium hydride source material that includes lithium hydride to
form liquid-phase lithium hydride. The methods generally also
involve reducing an ambient pressure over the liquid-phase lithium
hydride. Typically, a further step involves extracting hydrogen and
gaseous-phase lithium metal from the liquid-phase lithium hydride.
Generally the methods also involve condensing the gaseous-phase
lithium metal as solid-phase lithium metal. Then the solid-phase
lithium metal may be melted to form refined liquid-phase lithium
metal. Some methods may include hydriding the refined liquid-phase
lithium metal.
BRIEF DESCRIPTION OF THE DRAWINGS
Various advantages are apparent by reference to the detailed
description in conjunction with the figures, wherein elements are
not to scale so as to more clearly show the details, wherein like
reference numbers indicate like elements throughout the several
views, and wherein:
FIG. 1 is a somewhat schematic cross-sectional view of an apparatus
for processing hydrogen and lithium materials;
FIG. 2 is a vapor pressure curve for hydrogen in lithium hydride as
a function of temperature;
FIG. 3 is a vapor pressure curve for lithium metal as a function of
temperature; and
FIG. 4 is an exemplary temperature profile for extracting hydrogen
from lithium hydride and purifying the resultant lithium.
DETAILED DESCRIPTION
In the following detailed description of the preferred and other
embodiments, reference is made to the accompanying drawings, which
form a part hereof, and within which are shown by way of
illustration the practice of specific embodiments of hydrogen and
lithium material processing apparatuses and embodiments of methods
of processing hydrogen and lithium material. It is to be understood
that other embodiments may be utilized, and that structural changes
may be made and processes may vary in other embodiments.
Lithium hydride is a very space-efficient material for the storage
of hydrogen. The hydrogen density in lithium hydride is greater
than the density of metallic (solid) hydrogen. In other words there
is more hydrogen stored in a cubic unit measure of lithium hydride
than in the same cubic unit measure of pure metallic hydrogen. This
phenomenon provides a potential for the use of lithium hydride as a
means of compact storage of hydrogen for use in hydrogen-powered
vehicles and other applications where a source of hydrogen on
demand is needed.
At atmospheric pressure lithium hydride melts at about 692.degree.
C. By reducing the ambient pressure to near vacuum conditions,
lithium hydride may be melted at about 680.degree. C. At
atmospheric pressure liquid lithium hydride decomposes into lithium
metal and hydrogen gas at about 850.degree. C. The temperature at
which the decomposition occurs may be lowered to about 750.degree.
C. by reducing the ambient pressure over the liquid lithium hydride
to near vacuum conditions. These characteristics may be used in
thermal processes to generate hydrogen from lithium hydride with
relative safety compared with a chemical reaction of water with
lithium hydride. Such thermal processes have a further advantage of
producing lithium metal instead of the lithium hydroxide that
results from the chemical reaction of water with lithium hydride.
Typically, many impurities in the lithium hydride are removed
during these thermal processes such that a refined lithium metal is
produced. In addition, such thermal processes may be extended to
economically produce high purity lithium hydride by re-hydriding
the refined lithium metal.
FIG. 1 illustrates an apparatus 10 that may be used to generate
hydrogen and lithium metal, as well as to produce high purity
lithium and high purity lithium hydride. The apparatus 10 may also
be used to store hydrogen and release the stored hydrogen for
subsequent use. The apparatus 10 provides a hot zone 14, a moderate
zone 18, a cold zone 22, and an extraction zone 26. The apparatus
10 also includes a vacuum system 38 that is connected by an
extraction line 34 to the top of the extraction zone 26 through a
manifold 30. Typically the vacuum system 38 is an oil-free vacuum
pump. A valve 42 is typically provided in the extraction line 34 to
permit sealing off the vacuum system 38 from the extraction zone
26.
In the embodiment of the apparatus 10 depicted in FIG. 1 the hot
zone 14 includes a shim pot 46 that is disposed within a process
vessel 50. A "shim pot" is a double-walled vessel with a space
between the walls for containing materials. In the embodiment of
FIG. 1, a lithium hydride source material 58 is disposed between
the walls of the shim pot 46. In the embodiment of apparatus 10
depicted in FIG. 1, a center can 54 is disposed within the open
space formed by the inner wall of the shim pot 46. The shim pot 46
and the center can 54 are preferably constructed from a material
such as iron that is compatible with lithium. In some embodiments
the shim pot 46 is not used and the lithium hydride source material
58 is disposed between the process vessel 50 and the center can 54.
In such embodiments the process vessel 50 is preferably constructed
from a material such as iron that is compatible with lithium. In
embodiments where a shim pot is used (such as shim pot 46) the
process vessel 50 may be constructed from stainless steel, which
could be susceptible to erosion if contacted with hot lithium were
it not for the protection against such erosion that is provided by
the shim pot 46. Typically the shim pot 46, the process vessel 50
and the center can 54 are concentric circular annular shapes.
The lithium hydride source material 58 is substantially lithium
hydride, but the lithium hydride source material 58 may include up
to ten percent impurities. That is, the lithium hydride content may
be in a range from about ninety to one hundred percent of the
lithium hydride source material 58.
Typically the operation of the apparatus 10 begins with
establishing a flow of purge gas such as argon 62 from a tank 64
through the manifold 30. Then the vacuum system 38 is activated
with the valve 42 open. The purge flow tends to reduce the flow of
dust from the lithium hydride source material 58 into the vacuum
system 38. The process vessel 50 and the shim pot 46 (if used) and
the center can 54 are then heated with an appropriate energy source
(e.g., electric resistance, induction, natural gas). The hot zone
14 is kept under dynamic vacuum by the vacuum system 38 as the
temperature is increased. The term "dynamic vacuum" means that the
hot zone 14 is being actively pumped by the vacuum system 38 (i.e.,
it is not just pumped to vacuum and then valved off, leaving a
trapped vacuum condition). This active pumping removes the argon 62
and any off-gasses from the lithium hydride source material 58.
Heating continues until the lithium hydride source material reaches
at least 680.degree. C., which is a melting temperature of lithium
hydride at reduced atmosphere. Radiation baffles 66 are provided in
the embodiment of FIG. 1 to reduce the heat loss through the top of
the hot zone 14. Even so, when the bottom of the hot zone 14 is at
680.degree. C. the top of the hot zone 14 may only reach
400.degree. C. This is acceptable. Once the lithium hydride source
material 58 is melted the flow of purge gas (e.g., argon 62 through
the manifold 30) may be discontinued.
As this process proceeds, a barrier crust may form above the
liquid-phase lithium hydride in the shim pot 46 (or in the process
vessel 50 if the shim pot 46 is not used). The barrier crust is a
slag-like material that may be formed from impurities in the
lithium hydride, and from lithium hydroxide formed from lithium
hydride reacting with trace amounts of water vapor in the apparatus
10, and/or from other contaminants. The barrier crust slows down
the evolution of hydrogen from the liquid-phase lithium hydride. To
overcome this, FIG. 1 illustrates that the apparatus 10 may include
an agitator 70 for retarding the formation of the barrier crust. In
some embodiments the agitator 70 may comprise an inert gas sparge,
such as a gas sparge using a flow of the argon 62 that was
discontinued as a purge gas when the lithium hydride source
material 58 melted. Such a sparge flow substantially retards the
formation of the barrier crust above the molten phase. In some
embodiments the agitator 70 may comprise an energy source having a
periodic waveform (such as ultrasonic vibration) that is applied to
the bottom of the shim pot 46 to retard the development of a
barrier crust. In embodiments that do not employ the shim pot 46,
the agitator 70 is applied at the bottom of the process vessel 50
between the process vessel 50 and the center can 54.
After the lithium hydride source material 58 melts, the process
vessel 50 and the shim pot 46 (if used) and the center can 54 are
further heated such that the lithium hydride source material 58
reaches a temperature of at least 750.degree. C. At that
temperature, under near vacuum conditions, the molten lithium
hydride decomposes into lithium metal and hydrogen. FIGS. 2 and 3
illustrate the comparative vapor pressures of hydrogen in molten
lithium hydride (FIG. 1) versus the vapor pressure of lithium
metal. At any temperature in the range of 700.degree. C. to
1000.degree. C. the vapor pressure of hydrogen from lithium hydride
is ten to thirty times higher than the vapor pressure of lithium
vapor from lithium metal. Lithium hydride decomposes when the vapor
pressure of the hydrogen content is above about 30 torr. This
occurs at about 750.degree. C., and at that temperature the vapor
pressure of Li from lithium metal is about 1 torr. Consequently, at
750.degree. C., hydrogen is preferentially (almost exclusively)
generated, with very little lithium vapor generated. Typically at
750.degree. C., hydrogen generation occurs as fast as it can be
pumped until all of the lithium hydride in the lithium hydride
source material 58 has decomposed to lithium metal and
hydrogen.
As the lithium hydride decomposes into hydrogen and lithium metal,
the vacuum system 38 pulls the hydrogen along paths 74 through the
moderate zone 18. In embodiments where an inert gas sparge is
employed, the vacuum system 38 also pulls the inert sparge gas
through the moderate zone 18 and the cold zone 22.
The hydrogen (and inert sparge gas, if present) flows out of the
vacuum system 38 into an accumulator 94. Certain impurities may
also be pulled into the accumulator 94. A hydrogen membrane filter
98 (such as a side stream palladium filter) may be used to extract
hydrogen 102 (which is substantially pure after filtration) and
store it in a hydrogen storage compartment 114. The hydrogen 102
may be piped out of the hydrogen storage compartment 114 for use in
a fuel cell process or for use in other devices or chemical
processes. If an inert gas sparge (such as the argon 62) is used,
recovered inert gas 106 may be temporarily stored in an inert gas
storage compartment 110. The recovered inert gas 106 may then be
returned to the tank 64 and reused.
The just-concluded description of extraction of hydrogen from the
lithium hydride source material completes the process application
steps needed for some embodiments. In such embodiments the
apparatus 10 may be reused for multiple repetitive operations by
re-hydriding the lithium that remains in the hot zone 14. To do
this, the hot zone 14 with the refined lithium metal in the process
vessel 50 is heated to a temperature of about 800.degree. C. (if it
is not already at that temperature). Then hydrogen (at
approximately 16 psia) is introduced into the hot zone 14 from a
source of hydrogen 170, and the lithium metal is converted to
lithium hydride. With this approach the apparatus 10 provides a
reusable, high density hydrogen storage device. In such embodiments
the apparatus 10 may be simplified by eliminating the shim pot 46
and eliminating elements described and discussed later herein such
as the inclined deflector 78, the elements in the moderate zone 18,
and the elements of the cold zone 22.
In some embodiments it is desirable to purify the liquid-phase
lithium metal that remains in the process vessel 50 after
extraction of the hydrogen from the lithium hydride. To do this,
the process vessel 50 and the shim pot 46 (if used) and the center
can 54 are further heated to about 900.degree. C. At that
temperature the vacuum system 38 is able to extract gaseous-phase
lithium metal from the liquid-phase lithium in the hot zone 14. An
inclined deflector 78 may be provided to keep molten gaseous-phase
lithium metal from weeping to the sides of the radiation baffles
66, and falling back into the space between the shim pot 46 and the
center can 54. The deflector 78 is typically inclined at an angle
82 that is at least 12 degrees. In embodiments where the shim pot
46, the process vessel 50, and the center can 54 are annular, the
deflector 78 is generally conical-shaped. The use of the sparge gas
(e.g., the argon 62) encourages the formation of lithium vapor, and
because the lithium vapor is relatively heavy the sparge gas helps
to float the lithium vapor up to the top and out of the liquid
lithium where it is pulled by the vacuum system 38 into the cold
zone 22.
The cold zone 22 typically includes a chiller 122, such as a
counter flow gas to gas heat exchanger. The gaseous-phase lithium
metal pulled into the cold zone 22 solidifies as solid-phase
lithium metal in the cold zone 22. Some of the gaseous-phase
lithium metal vapors passing through the moderate zone 18 may
condense back to liquid-phase lithium metal in the moderate zone 18
before reaching the cold zone 22. This condensed liquid-phase
lithium metal (lithium metal condensate) flows by gravity back down
through the funnel-shaped portion 130 of the moderate zone 18 to
the center can 54 in the hot zone 14. Upon its return to the
process vessel 50 the condensed liquid-phase lithium metal is again
converted to gaseous-phase lithium metal. Eventually all
gaseous-phase lithium metal vapors pass through the moderate zone
18 and condense in the cold zone 22 where the lithium metal is
trapped in the solid phase.
FIG. 3 presents a summary of an exemplary temperature profile that
may be used to extract hydrogen and lithium metal from the lithium
hydride source material 58. The process starts at point "A" where
the process vessel 50 is heated and argon 62 is introduced as a
purge gas through the valve 42. When the lithium hydride source
material 58 reaches a temperature of about 680.degree. C. (at point
"B") and is molten, the flow of argon 62 is switched to a sparge
gas through the agitator 70. During the time interval "C" the
lithium hydride becomes molten. The temperature of the molten
lithium hydride is then increased to about 750.degree. C. and
during time interval "D" the lithium hydride decomposes to lithium
and hydrogen, and the hydrogen is pumped away. When the lithium
hydride decomposition is complete (at time "E") the molten lithium
is further heated to about 900.degree. C. where, during time
interval "F," the lithium metal vaporizes and is frozen in the cold
zone 22.
Upon completion of the thermal decomposition of lithium hydride and
the deposit of the solid-phase lithium metal in the cold zone 22,
the gas pressure in the device approaches full vacuum (provided
that the inert gas sparge, if used, is turned off). At that point,
the valve 42 to the vacuum system 38 may be closed and the
apparatus 10 may be cooled, typically by simply turning off power
to the apparatus 10.
The highly purified lithium metal that has condensed in the cold
zone 22 may be extracted by using heaters 146 to heat the cold zone
22 to a temperature above 180.degree. C., the melting temperature
of lithium metal. Supplemental heaters 150 may be applied to the
moderate zone 18. The purified liquid-phase lithium metal runs down
into the center can 54 of the hot zone 14 (which is now cold)
through a cylinder 158, thereby providing refined lithium metal.
The cylinder 158 has an end 162, and it beneficial to have the end
162 of the cylinder 158 terminate at an elevation that is below the
top of the center can 54.
As previously noted, the apparatus 10 may be recharged for
repetitive operations by re-hydriding the refined lithium in the
hot zone 14 such that the refined lithium metal is converted to
refined lithium hydride. Alternately, the vapor distilled,
ultra-high purity refined lithium metal may be removed from the
process vessel 50 under inert conditions for other uses. In some
embodiments the apparatus 10 is used as a reiterating lithium or
lithium hydride refining device, and in such embodiments the source
of hydrogen 170 may include hydrogen 102 extracted from a prior
decomposition of lithium hydride.
In addition to various embodiments of apparatuses, the present
disclosure provides methods of processing hydrogen and lithium
material. The methods typically involve heating a lithium hydride
source material that includes lithium hydride to form liquid-phase
lithium hydride. The lithium hydride source material is heated to a
temperature that is typically in the range of 750.degree. C. to
800.degree. C. to form a liquid-phase lithium hydride. A reduced
ambient pressure over the liquid-phase lithium hydride (such as
provided by a vacuum pump) extracts hydrogen and gaseous-phase
lithium metal from the liquid-phase lithium hydride as the lithium
hydride decomposes. The reduced ambient pressure also has a benefit
of reducing the decomposition temperature of the lithium hydride.
Typically the gaseous-phase lithium metal is condensed as
solid-phase lithium metal. Sometimes a lithium condensate portion
of the gaseous-phase lithium may be captured and returned to the
lithium hydride source material as liquid-phase lithium condensate.
The solid-phase lithium metal may be extracted from the cold zone
by melting to form refined lithium metal, and the refined lithium
metal may be hydrided using hydrogen gas to form a re-charged
lithium hydride. The previously-described process steps for
decomposing lithium hydride may then be repeated one or more times
using recharged lithium hydride as the lithium material.
Some processes may involve retarding the formation of a barrier
crust that may form adjacent the liquid-phase lithium hydride. This
retarding step may involve sparging the liquid-phase lithium
hydride with an inert gas such as argon, and/or it may involve
agitating the liquid-phase lithium hydride with an energy having a
periodic waveform, such as ultrasonic energy.
In summary, embodiments disclosed herein provide a hydrogen and
lithium material processing apparatus and methods of processing
hydrogen and lithium materials. The foregoing descriptions of
embodiments have been presented for purposes of illustration and
exposition. They are not intended to be exhaustive or to limit the
embodiments to the precise forms disclosed. Obvious modifications
or variations are possible in light of the above teachings. The
embodiments are chosen and described in an effort to provide the
best illustrations of principles and practical applications, and to
thereby enable one of ordinary skill in the art to utilize the
various embodiments as described and with various modifications as
are suited to the particular use contemplated. All such
modifications and variations are within the scope of the appended
claims when interpreted in accordance with the breadth to which
they are fairly, legally, and equitably entitled.
* * * * *